Recording media, e.g. DVDs, on which copyrighted works such as movies and music are recorded in digital form, are widely used in recent years.
DVDs employ a system called CSS (Content Scrambling System) for protecting content from unauthorized copying. According to CSS, information unique to a DVD is stored on the DVD, and a title key is created from this information and information held in a player. Encrypted content recorded on the DVD is decrypted using this title key, and the decrypted content is played back (see Japanese Patent Application Publication H05-257816 as one example).
Meanwhile, a content delivery system that uses DRM (Digital Rights Management) is becoming common in recent years. According to DRM, a license is provided separately from encrypted content. The license contains a license key and a use condition. The encrypted content is decrypted using the license key and the decrypted content is played back, based on the use condition.
In DRM, content and a license are distributed via a network. Further, attempts are recently being made to distribute content using a storage-type broadcast system called server broadcasting.
In view of this, there is a growing need to suitably apply DRM to content distribution that utilizes recording media such as the above.